Fighters from a US-backed, Kurdish-led coalition battled Syrian government forces in northeast Syria early on Tuesday, both sides said, opening a new front for President Bashar al-Assad who lost Aleppo in a sudden advance by armed opposition groups last week.Airstrikes also targeted Iran-backed militia groups supporting Syrian government forces in the strategically vital region, a security source in eastern Syria and a Syrian army source said.The sources both blamed the airstrikes on the US-led military coalition which operates against ISIS in Syria and has a small detachment of American troops on the ground. Reuters could not independently confirm the foreign force was involved in strikes and the coalition did not immediately respond to a message seeking comment.For all the latest headlines follow our Google News channel online or via the app.Last week’s assault that captured Aleppo - Syria’s largest city before the war - is the biggest offensive for years in a conflict whose